After
many thousands of years your planet will
become a world with a solid surface.

We know that climate tends to
get cooler as we move away from the equator toward the poles.

As the planet curves, the sun's
rays cover more ground, and the sun's heat is diluted. See
how the beam spreads over the slanting roof.

At the equator, the sun's rays
meet the planet straight on, like hitting the side of a house.
The heat is more concentrated here.

As
the climate changes, the biomes change, too.

You
can experience climate
change without going on a trip to the north or south.
Temperatures change with changes in altitude.The temperature of the atmosphere
drops three degrees Fahrenheit for every 1000 feet in elevation
rise.

This is why people go to the
mountains in the summer: they are looking for cooler temperatures.

In this picture below, we see
examples of temperature and biome change.

We are pretty close to the equator
here. Where the ocean meets the land there is heavy rain, and
a beautiful tropical rain forest covers the ground.

Next comes an area where the
tropical rain forest blends into the deciduous forest. As we
go up the mountain the vegetation types blend into each other,
and before too long we are in a typical deciduous forest with
trees that we would expect to see farther north. Because of
cooler winters these trees will lose their leaves in the fall.
The cooling air releases rain as it rises.

As the elevation continues to
rise, the deciduous forest gives way to an evergreen coniferous
forest. Here we find trees and bushes that we would normally
see much farther north. These trees gradually become shorter
and are spaced farther apart as the forest gives way to a grassy
alpine biome. Here marmots whistle among the grasses and wild
flowers.

Eventually, grass gives way
to rocks, stones, and snow. The wind is cold up here, and we
are feeling the lack of oxygen in the thin air. We stop to
pant after climbing only a few steps.

At 20,000
feet we are at what climbers call the Death Zone because brain cells
are beginning to die from lack of oxygen in the air. They can
survive for a few hours but should not stay here long without
bringing and using oxygen cylinders and a breathing mask.

I hope that the people in the
balloon have some oxygen with them, or else are planning to come
down very, very soon. They could easily die up there because there
is not enough oxygen in this thinning atmosphere for them.

It is because of this change
of temperature with altitude that high mountains are snow-capped
even at the equator.